U.S. patent number 4,454,372 [Application Number 06/255,312] was granted by the patent office on 1984-06-12 for photovoltaic battery.
This patent grant is currently assigned to Electric Power Research Institute, Inc.. Invention is credited to Anthony J. Appleby.
United States Patent |
4,454,372 |
Appleby |
June 12, 1984 |
Photovoltaic battery
Abstract
A photovoltaic cell in which a plurality of semiconductor bodies
are provided on a conductive layer on a major surface of a
substrate. Each body includes a core and an outer layer of
different conductivity types. A transparent conductive layer
interconnects the semiconductor bodies. In one embodiment a single
conductive layer is formed on the substrate, and a voltage
differential is generated between the signal conductive layer and
the transparent conductive layer. Alternatively, two conductive
layers can be provided on the substrate and the voltage
differential is generated between the two conductive layers.
Inventors: |
Appleby; Anthony J. (Mountain
View, CA) |
Assignee: |
Electric Power Research Institute,
Inc. (Palo Alto, CA)
|
Family
ID: |
22967756 |
Appl.
No.: |
06/255,312 |
Filed: |
April 17, 1981 |
Current U.S.
Class: |
136/250;
257/E27.124; 257/E31.038 |
Current CPC
Class: |
H01L
31/022425 (20130101); H01L 31/0504 (20130101); H01L
31/035281 (20130101); Y02E 10/50 (20130101) |
Current International
Class: |
H01L
27/142 (20060101); H01L 31/0224 (20060101); H01L
31/0248 (20060101); H01L 31/0352 (20060101); H01L
031/06 () |
Field of
Search: |
;136/250 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Weisstuch; Aaron
Attorney, Agent or Firm: Flehr, Hohbach, Test, Albritton
& Herbert
Claims
What is claimed is:
1. A photovoltaic battery comprising
a substrate,
a plurality of conductive layers formed on a major surface of said
substrate, said plurality of conductive layers being alternately
interdigitatedly arranged and spaced from each other,
a plurality of first type discrete semiconductor bodies positioned
on one side of each of said plurality of conductive layers, each of
said plurality of first type discrete semiconductor bodies
including a first region of a first conductivity type and a second
region of a second conductivity type, said first and second regions
defining a PN junction, said first region contacting one of said
conductive layers,
a plurality of second type discrete semiconductor bodies positioned
on an opposite side of each of said pluralities of conductive
layers, each of said plurality of second type discrete
semiconductor bodies including a first region of said first
conductivity type and a second region of said second conductivity
type, said first and second regions defining a PN junction, said
second region contacting one of said conductive layers,
a plurality of third type transparent conductive layers overlying
said pluralities of first and second type discrete semiconductor
bodies and electrically interconnecting said second regions of said
plurality of first type semiconductor bodies and said first regions
of said plurality of second type semiconductor bodies whereby
photons impinging on said semiconductor bodies generate a voltage
between adjacent ones of said plurality of conductive layers.
Description
This invention relates generally to semiconductor technology and
devices, and more particularly the invention relates to
semiconductor photovoltaic cells.
Semiconductor photovoltaic devices are known which respond to solar
radiation and generate an electrical charge or current. The silicon
cell as employed in solar batteries has a p-n junction across which
a voltage differential is developed in response to impinging
photons. Heretofore, manufacturing costs of the silicon cell and
the low conversion efficiency thereof have limited utility of the
silicon cell.
In recent years, the solar cell has been proposed for use in
producing chemical energy rather than electrical energy. For
example, such a cell may be in permanent contact with an
electrolytic solution, and an electrical current generated by the
solar cell and flowing through the electrolytic solution produces
chemical products. At least one of the chemical products may
typically be in gaseous form, and the chemicals evolving from the
solar cell can be captured for subsequent use in thermal conversion
or in a fuel cell device where the chemicals are recombined to
generate an electrical current.
U.S. Pat. No. 4,021,323 discloses a solar energy conversion system
in which doped silicon beads are placed in contact with a solution
whose decomposition potential is sufficiently low so that the
solution can be efficiently photodecomposed with the chemicals
stored and later recombined in a fuel cell. U.S. Pat. No. 4,173,494
describes techniques for fabricating devices of the type disclosed
in U.S. Pat. No. 4,021,323 and particularly the method of forming
discrete semiconductor bodies including a core of first
conductivity type and an outer layer of second conductivity type.
The cores and outer layers of a mixture of particles of different
core conductivity type contact an insulated conductive layer and an
electrolytic solution in the devices whereby a voltage potential is
produced across the electrolyte so that chemical species are
produced by its decomposition.
Copending application Ser. No. 205,617, filed Nov. 10, 1980,
assigned to the present assignee, now U.S. Pat. No. 4,357,400,
discloses a photovoltaic cell employing discrete semiconductor
bodies, similar to the structures in U.S. Pat. No. 4,021,323, and
4,136,436, and which is used with an electrolytic solution for
generating electrical energy. A plurality of discrete semiconductor
bodies are positioned on two conductive layers whereby radiation is
transmitted through the electrolytic material to the semiconductor
bodies to create a voltage differential and whereby the
electrolytic material provides a conductive path between the
semiconductor bodies.
An object of the present invention is an improved photovoltaic
cell.
Another object of the invention is a photovoltaic cell comprising a
plurality of discrete semiconductor bodies without the requirement
for an electrolytic solution.
A feature of the invention is the use of a transparent conductive
layer overlying and electrically interconnecting a plurality of
discrete semiconductor bodies with each of the semiconductor bodies
comprising a first region of first conductivity type and a second
region of second conductivity type which define a PN junction.
Briefly, in accordance with a first embodiment of the invention a
photovoltaic cell comprises a substrate with a first conductive
layer on a major surface of the substrate. A plurality of discrete
semiconductor bodies are positioned on the first conductive layer
with each of the discrete bodies including a first region of first
conductivity type and a second region of second conductivity type
with the first and second regions defining a p-n junction. The
first region of each semiconductor body abuts the first conductive
layer. A second, transparent conductive layer overlies the
plurality of discrete semiconductor bodies and electrically
interconnects the second regions whereby photons impinging on the
semiconductor bodies generate a voltage between the first and
second conductive layers.
In accordance with an alternative embodiment of the invention a
substrate is provided with a first conductive layer and a second
conductive layer on a major surface with the first and second
conductive layers being spaced from each other. A first plurality
of discrete semiconductor devices are positioned on each of the
first conductive layers with each of the first plurality of
discrete semiconductor devices including a first region of first
conductivity type and a second region of a second conductivity
type. The first region of the first plurality of discrete
semiconductor bodies abuts the first conductive layer. A second
plurality of discrete semiconductor bodies is positioned on the
second conductive layer, with each of the second plurality of
discrete semiconductor bodies including a first region of said
first conductivity type and a second region of said second
conductivity type with the second region of the second plurality of
bodies abutting the second conductive layer. A third, transparent
conductive layer overlies the first and second pluralities of
discrete semiconductor bodies and electrically interconnects the
second regions of the first plurality of bodies with the first
regions of the second plurality of semiconductor bodies whereby
photons impinging on the semiconductor bodies generate a voltage
between the first conductive layer and the second conductive layer
formed on the major surface of the substrate.
In either embodiment, an insulative material such as glass is
preferably provided over the major surface between the plurality of
discrete semiconductor devices.
The invention and objects and features thereof will be more readily
apparent from the following detailed description and appended
claims when taken with the drawing, in which:
FIG. 1 is a plan view of a portion of a photovoltaic cell in
accordance with one embodiment of the invention.
FIG. 2A is a section view of the photovoltaic cell of FIG. 1 taken
along the line 2--2.
FIG. 2B is a section view of an alternative embodiment of a
photovoltaic cell taken along the line 2--2 of FIG. 1.
FIGS. 3A and 3B are plan views of portions of solar panels using
the photovoltaic cells of FIG. 2B.
FIG. 4 is a section view of an alternative embodiment of the
semiconductor bodies for use in the photovoltaic cell of FIG.
1.
Referring now to the drawings, FIG. 1 is a top view of a portion of
a photovoltaic cell in accordance with the invention and includes a
plurality of generally spherical semiconductor bodies 12 which are
supported by a substrate with an overlying layer of conductive
material 14 contacting and electrically connecting the
semiconductor bodies 12. Preferably, the conductive layer 14 is a
material such as tin oxide which is transparent to photons. In one
embodiment of the invention a conductive grid 16 of aluminum or
other low resistance material is provided over the conductive layer
14 with the grid pattern provided between adjacent semiconductor
bodies 12. The grid patttern 16 is advantageous when the overlying
conductive layer 14 functions as one terminal of the photovoltaic
cells, as will be described with reference to FIG. 2A.
FIG. 2A is a section view of the photovoltaic cell of FIG. 1 taken
along the line 2--2 in which each of the semiconductor bodies 12
comprises a first region 18 of P type conductivity and an overlying
layer 20 of N type conductivity. Each of the spheres is positioned
on a conductive layer 22 such as aluminum on a major surface of a
supporting substrate 24 such as glass or a ceramic. An insulative
material 26, such as glass, is provided over the surface of the
conductive layer 22 between the semiconductor bodies 12.
Photons transmitted through the transparent conductive layer 14 and
impinging on the semiconductor bodies 12 generate an electrical
potential between the conductive layers 14 and 16 (negative) and
the conductive layer 22 (positive). The device is similar to the
photovoltaic cells shown and described in copending application
Ser. No. 205,617, supra, except that the electrolytic solution
utilized in the device disclosed in the copending application is
replaced by the transparent conductive layer 14.
FIG. 2B is a sectional view of an alternative embodiment of the
device of FIG. 1 taken along the line 2--2 and in which the grid 16
is not required. In accordance with this embodiment a first
plurality of semiconductor bodies 30 having an N type conductivity
core and an overlying P layer are mounted on a first plurality of
interconnected conductive layers 32 on the surface of a substrate
34 with the N conductivity cores in contact with the conductive
layers 32. A second plurality of discrete semiconductor bodies 36
having a P type core and an N type outer layer are positioned on a
second plurality of interconnected conductive layers 38 on the
surface of substrate 34 with the P type material abutting the
conductive layers 38. The conductive layers 32 and 38 are spaced
from each other on the surface of the substrate. A thin layer of
reflective material 40 can be provided on the opposite surface as
substrate 34 to reflect photons back to the semiconductor bodies
30, 36.
Again, an insulative material 42 such as glass is provided on the
surface of the transparent base plate 34 between the semiconductor
bodies 30, 36, and a transparent conductive layer 44 such as tin
oxide is provided over the surfaces of the semiconductor bodies 30
and 36. In this embodiment photons transmitted through the
conductive layer 44 impinge on the semiconductor devices and create
a voltage differential between the conductors 32 (negative) and the
conductors 38 (positive). The devices as shown in FIGS. 2A and 2B
can be fabricated in accordance with the teachings of copending
application No. 205,617 and U.S. Pat. No. 4,136,436.
FIGS. 3A and 3B are plan views of portions of solar panels using
the photovoltaic cells of FIGS. 2B. In FIG. 3A interdigitated
conductive layers 50, 51, 52, and 53 are provided on an insulative
substrate with the P conductive core semiconductor bodies provided
on the left extension of each conductive layer, and the N
conductive core semiconductor bodies provided on the right
extensions of each conductive core. Each conductive layer then
becomes a cell of the solar panel. A transparent conductive film 55
such as tin oxide then serially interconnects adjacent cells.
FIG. 3B is similar to FIG. 3A and the same reference numerals are
used for like elements. However, in this embodiment the conductive
layers 50, 51, 52 and 53 are not interdigitated.
FIG. 4 is a section view of a semiconductor body illustrating an
alternative construction of the photovoltaic cells. This embodiment
is similar to that illustrated in FIG. 2B but with the outer layer
62 of the semiconductor body 60 abutting the conductive layer 64 on
substrate 66 and the transparent conductive material 68 abutting
the P type core material 70. Again, an insulative material 72 such
as glass is provided on the surface of the substrate 66 between the
semiconductor bodies 60. After affixing the semiconductor bodies to
the conductive layers on the substrate, an etchant is applied to
remove the outer N type layer away from the conductive layer. Glass
insulation is then provided to seal the N type layer before the tin
oxide layer 68 is formed. An advantage of the structure in
accordance with FIG. 4 lies in the internal reflectivity of each
semiconductor body which further enhances the conversion of the
photons to electrical energy. Accordingly, a greater conversion
efficiency is realized with this structure.
Photovoltaic cells and solar panels in accordance with the
invention are readily constructed and obviate the need for an
electrolytic solution. While the invention has been described with
reference to specific embodiments, the description is illustrative
of the invention and is not to be construed as limiting the
invention. Various modifications and applications may occur to
those skilled in the art without departing from the true spirit and
scope of the invention as defined by the appended claims.
* * * * *